Method oe preventing gas explosions in blast-etjrnaces during temporary



J. W. DOUGHERTY.

METHOD OF PREVENTING GAS EXPLOSIONS IN BLAST FURNACES DURING TEMPORARY STOPS.

APPLICATION FILED MAR. 20. I919.

1,309,466. Patented July 8, 1919.

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JOHN W. DOUGHERTY, OF BEAVER, PENNSYLVANIA.

Specification ofI-etters Patent.

Patented July 8, 1919.

Application filed March 20, 1919. Serial No. 283,841.

able others skilled in the art to which it ap crtains to make and use the same.

y invention relates to the prevention of explosions in blast furnaces and the auxiliary parts of blast furnace systems during a stop for temporary repairs, and the starting up after a stop for such repairs, and it consists in driving out the gas from the auxiliary partsv of the furnace system by means of a non-explosive gas (which, of course, includes steam, nitrogen, carbondioxid, or any other inert gaseous medium desired, or convenient to be introduced).-

This inert medium is for the purpose of driving out the gas from the auxiliary parts and apparatus of the furnace and confining the gas to the furnace without admitting air, and this I do by admitting such medium, preferably steam because it is the cheapest and most convenient, to the dustcatcher, during astop for repairs, so as to produce an outward pressure in the dustcatcher and its adjacent parts, and at the same time produce a counter pressure at the bottom of the down-comer, so as to confine the gases within the blast furnace itself. I thus produce a few ounces of steam pressure behind the gas in the down-comer that follows up or compensates the loss of volume due to leakage, thereby preventing any air from leaking into the dust-catcher or throughany other part adjacent thereto,

'such as the gas mains, valves, or the like,

whereby the explosive mixture could or might be formed.

For example, I drive the gas out of the furnace system or parts of the furnace system by means of the steam. In case of repairs, such as the replacement of a bell, steam is admitted to the dust-catcher, or to pipes adjacent thereto to drive gas from the down-comer out from the top of the furnace, and in quantities suflicient to maintain an outward pressure in the dust-catcher.

When the bell is closed for the purpose of replacing a twyer, steam is admitted to the dust-catcher, or to any other part of the system between the boiler and hot blast stoves and the shaft of the furnace, to maintain an outward pressure and to prevent any gas from entering the dust-catcher or other leaky parts of the gas system, the gas being driven out of the pipe lines by means of steam pressure. The air is thus prevented from entering the down-comer and thence into the top of the furnace, by reason of the steam pressure confining the gases within the furnace and preventing the entrance of air at all points of'the system by maintaining an outward steam pressure on the system.

In replacing a leaking twyer or the twyer cooler, steam pressure is maintained in the dust-catcher, for the reason that when this operation is taking place it is found expedient to connect the twyers through the bustle pipe and hot blast pipe to the stack by opening a hot blast valve and the draft valve of one of the stoves, the gas valve and cold blast valve having been previously closed. By doing this, the stove stack pulls directly on the interior of the furnace at the twyers and draws the gas away which would otherwise pufi out the opening in the furnace made while a twyer or cooler is being changed. This pull may be sufficient to also draw gas down from the top of the furnace while this drafting operation on the twyersis taking place.

The effect of this at the down-comer and dust-catcher will be the removal of some of the gas from the dust-catcher, and cause some air to be admitted to the catcher or other part of the system if steam is not maintained in the dust-catcher and systeni sufficient to keep up an outward pressure.

I have heretofore used steam as a plug or insert between a column of as and a column of air with the steam movlng ahead of the gas and following the air in blowing in a blast furnace.

The problem that I have solved in the present instance is to overcome explosions dueto an entirely different type of operations, and I have discovered that it may be done with steam, but in this instance the steam is located behind the column of gas, or inserted between two columns of gas in the blast furnace gas system, so as to follow up or drive the gas ahead of it and prevent the air from following along and entering the system and thus forming an explosive mixture with the hot gas.

The point of introduction of the steam into the gas system may be anywhere between the two ends of the system, that is, any. point between the inlet end, or shaft of the furnace, and the outlet end, at the boiler and hot blast stoves.

I have diagrammatically illustrated the invention in the accompanying drawings, in which like parts are similarly designated.

Figure 1 is a diagrammatic elevation of so much part of a blast furnace system as is necessary, showing pointsof steam introduction. I

Fig. 2 is a diagrammatic plan of a blast furnace system, on a smaller scale. The blast furnace is indicated by a, the downcomer by b, the dust catcher by c, the gas main by d, the hot blast main by e, and the bustle pipe by f.

The gas and the hot blast mains d and e have connected to them various branch pipes, and it is preferable, but not necessary, to make the connections-for admitting steam into the gas system between the inlet end of the system where the down-comer 1) leaves the furnace a and that point of the gas main 0) where it connects the branch pipes to the other; devices.

I have shown the steam pipes g and h to the down-comer near its beginning at the furnace at l, and other steam inlets 2, 3 and 4 to points of the gas conduit, as dust catcher and gas main, after leaving the latter.

Any number of such steam inlets may be applied to the gas system between the furnace and the auxiliary apparatus.

In Fig. 2 these connections may be more readily seen with respect to the hot blast stoves, stack and boilers, the boilers furnishing the steam for the plant.

I claim- 1. The method of preventing explosions during a temporary stop in the operation of blast furnace systems, which comprises introducing steam into the gas system at a point between the hot blast stoves and the shaft of the furnace, thereby maintaining a volume of steam between the points of air admission to the system and the gas, the movement of which steam shall be in the direction of movement of the gas.

neoence 2. The method of preventing explosions during a temporary stop in the operation of blast furnace systems, which comprises introducing steam into the gas system at a point between the hot blast stoves and boiler burners and the shaft of the furnace, thereby maintaining a volume of steam between the points of air admission to the system and the gas, the movement of which steam shall bein the direction of movement of the gas.

3. The method of preventing gas explosions inblast furnaces during a temporary stop, 7. which comprises maintaining behind a gas volume in the furnace system a volume of steam above atmospheric pressure.

4. The method of preventing gas explosions in blast furnaces during a temporary stop, which comprises maintaining behind a gas volume in the furnace system a volume of inert gas above atmospheric pressure- I 5. The method of preventing gas explosions in blast furnaces during a temporary stop, which comprises introducing an inert gas above atmospheric pressure into the sysmm at a point between the points of outflow of gas in opposite directions, and maintaining said pressure while compensating the loss of gas volume in the system during the stop.

6. The method of preventing gas explosions in blast furnaces during a temporary stop, which comprises introducing steam above atmospheric pressure into the system at a point between the points of outflow of gas in opposite directions, and maintaining said pressure While compensating-the loss of gas volume in the system during the stop.

7. The method of controlling gas explosions in blast furnaces, which comprises introducing-an inert. gas under pressure about at the dust catcher of the furnace gas system, and maintaining such pressure during a temporary stop and while drafting the twyers through the hot blaststove stack.

8. The method of controlling gas .explosions in blast furnaces, which comprises introducing steam under pressure at about the dust catcher of the furnace gas system, and maintaining such pressure during a temporary stop and while drafting the twyers through the hot blast stove stack.

In testimony that I claim the foregoing as my invention, I have signed my name hereto.

JOHN w. norounn'rr. 

